1. Field of the Invention
This invention is related to the recovery of shale oil. More specifically, this invention provides a process for recovering kerogen from oil shale and converting the kerogen into shale oil. The utility of this invention lies in the process of recovering a superior quality shale oil from oil shale and the disposal of nontoxic shale rock tailings.
2. Description of the Prior Art
Kerogen is a bituminous substance present in the matrix of oil shale. The recovery of kerogen from the oil shale, and the subsequent refining of the kerogen to give shale oil, is well known in the art. Typical prior art processes for obtaining shale oil from oil shale concern mining and crushing of the oil shale, retorting of the crushed shale, and recovery of shale oil from the retort. Conventional retorting processes result in the production of a large volume of hot, partially clinkered residual shale containing varying amounts of sintered carbonaceous material, and gaseous by-products from the retort, typically containing compounds of hydrogen, hydrocarbons, carbon as coke, nitrogen, and sulfur. All of these products are environmentally undesirable. A certain percentage of the hydrocarbon values in the shale oil are consumed in the retorting process as fuel to provide the temperature needed in the retort. Also, it is well known that in the process of retorting, free oxygen from the air used to generate retort heat dissolves in the shale oil product, thereby lowering its quality. The maintenance costs involved in the crushing and retorting of the rock in retort processes increase the cost of recovery of the resultant shale oil. Furthermore, because the retort is not pressurized, the gaseous products are lost. The coke is also lost with the sintered tailings. All of these losses may amount to about fifty percent (50%) of the organic kerogen originally in the shale.
U.S. Pat. No. 3,726,784 by Correa et al. relates to the hydrotreating of a liquid product produced by liquefying coal; and more particularly, to processes wherein the liquefaction zone, in which coal is liquefied, and the hydrotreating zone, in which liquefied coal is hydrotreated, are both operated at essentially equivalent pressures. U.S. Pat. No. 4,018,663 by Karr provides a coal liquefaction process for converting coal to crude petroleum refinable by conventional petroleum refining techniques to produce gasoline and/or diesel fuel. U.S. Pat. No. 4,083,769 by Hildebrand et al. teaches a process for converting ash-containing raw coal to deashed coal liquids in preference to deashed coal solids. U.S. Pat. No. 4,190,518 by Giannetti et al. discloses a process for producing from coal an upgraded solid material which is solid and/or semi-solid at room temperature and which is capable of later being combined with a liquid for further uses. U.S. Pat. No. 4,255,248 by Rosenthal et al. provides a process wherein subdivided coal is dissolved in a process-derived solvent having a low heptane insoluble content and is subsequently hydrocracked under specified process conditions. U.S. Pat. No. 4,410,415 by Seitzer discloses a method for lowering the pourpoint of a shale oil obtained by retorting oil shale. The method involves contacting the shale oil with fresh, unretorted oil shale, preferably at elevated temperatures. U.S. Pat. No. 4,348,274 by Guerre relates to a process for the upgrading or beneficiation of oil shale and is particularly concerned with upgrading raw oil shale by physically removing a substantial portion of the lower grade shale particles through the use of gravimetric separations. U.S. Pat. No. 4,075,081 by Gregoli teaches a process for extracting oily constituents from oil shale by eliminating the retorting stage of conventional shale upgrading.
What is needed and what has been invented by me is a process for the production of kerogen from shale oil which does not include the deficiencies of conventional processes and which is not taught or suggested by the prior art.